In general, a vehicle engine includes a cylinder block including a plurality of cylinder bores through which a piston may be reciprocated and a cylinder head coupled to an upper part of the cylinder block to form a combustion chamber along with the piston and including a plurality of intake and exhaust ports for an installation for various kinds of intake and exhaust valves.
In the engine, a water-jacket for flowing cooling water to a circumference of the cylinder bore, a circumference of the combustion chamber, and a circumference of the intake and exhaust ports are installed in the cylinder block and the cylinder head. The water-jacket guides the flow of cooling water discharged from a water pump to the whole area in the cylinder block and the cylinder header to keep an operating temperature of the engine normal over the whole operation area of the engine.
That is, the water-jacket servers as a flow passage of cooling water to prevent main parts such as the cylinder block, the cylinder head, and the piston from suffering from thermal damage due to heat of maximum temperature (approximately 2500° C.) generated during a combustion process of a gas mixture within the combustion chamber.
Hereinafter, the existing water-jacket of the cylinder head will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram illustrating the problem of the related art. Referring to FIG. 1, the existing water-jacket of the cylinder head is formed at an intake side and an exhaust side in a length direction of the cylinder head. That is, the cooling water in the existing water-jacket of the cylinder head forms a parallel-flow. Therefore, the flow of cooling water cooling each cylinder is non-uniform. Further, when the cylinder is cooled by the parallel-flow, the deviation in the surface temperature between the cylinder first cooled with the cooling water due to an increase in cooling water temperature and the cylinder finally cooled occurs. Therefore, it is difficult to efficiently control the engine.
Further, a passage is formed to pass two flows of cooling water forming the parallel-flow therethrough, and therefore, cross sectional areas of the respective passages are increased. Therefore, there is a problem in that the flow of cooling water is not concentrated around the combustion chamber to be concentratedly cooled, and therefore, the cooling efficiency may be reduced.
Further, the two flows of cooling water forming the parallel-flow are discharged to the outside of the cylinder header through one outlet for cooling water to cause the resistance of the flow of cooling water, thereby reducing the cooling efficiency.